This invention relates to an integrated semiconductor device including a frequency divide-by-two circuit which comprises an inverter stage P.sub.1 and a switch T.sub.2 which is controlled by an input signal E at the frequency f.sub.0.
The invention is used in the construction of integrated microwave circuits on gallium arsenide, in particular in the construction of stabilized frequency sources or of programmable dividers permitting the synthesis of a set of stabilized frequencies.
It is generally known from the prior art that a frequency divide-by-two circuit constructed in dynamic mode, comprising an inverter stage, a follower stage and a switch stage, is limited by the propagation time (tpd) of a gate.
Such a divider circuit is described in the publication entitled "26 GHz GaAs Room-Temperature Dynamic Divider Circuit" by J. F. Jensen, L. G. Salmon et al in "GaAs Ic Symposium, pp. 201-204" ref. CH 2506-4/87/0000-0201, 1987 IEEE.
This document relates to a frequency divide-by-two circuit operating dynamically and which is based on the use of depletion field-effect transistors exhibiting a pinch-off voltage of approximately -2.5 V. This divider is composed of two stages (see FIG. 5 of the cited document).
The first stage is formed by a switching transistor controlled by a first clock signal .phi., followed by an inverter gate of BFD type. The second stage is formed by a switching transistor controlled by a second, complementary clock signal .phi. followed by a follower gate.
This known circuit exhibits the advantage of being capable of being constructed by means of a small number of transistors. However, in the technical field of applications envisaged, it still exhibits a certain number of disadvantages. In particular, the maximum frequency is limited by the propagation time of the two gates, this maximum frequency being expressed by the relation EQU F.sub.m ax=1/2tpd.
As the logic states are stored by charging or by discharging the gate capacitors of the inverter and follower transistors, the results of this is that charge propagation times (tpd) of less than 15 ps, which are required in order to divide signals emitted at frequencies greater than 30 GHz, are impossible to obtain in the present state of the art by means of this type of divider.
Another type of divider is known which makes use of a concept of regenerating capacity of a signal. This principle necessitates an amplification, the mixing, a feedback at the divided frequency and a filtering. Such a circuit is described in the publication entitled "Regenerative Frequency Division with a GaAs FET" by C. RAUSHER in "IEEE Transactions on Microwave Theory and Techniques, vol. MTT-32, No. 11, November 1984, pp. 1461-1468". The principal limitations of this known circuit reside in the fact that the transistor must be biased close to its pinch-off voltage in order to obtain the mixing which is necessary for the operation of the divider. This necessitates rather precise regulating components. Furthermore, this known circuit exhibits conversion losses.